U.S. Pat. No. 4,827,812 discloses a pocket screwdriver having a tubular shank with a distal bore portion for driving a standard removable screwdriver bit, an intermediate bore portion for storing a standard removable screwdriver bit, and a proximal portion which is closed by a torque cap. The torque cap is in the form of a rod inserted in the bore and after being removed from the bore can be inserted through diametrically opposite holes formed in the wall of the proximal portion to amplify the torque applied by the tubular shank.
However the torque cap adds significantly to the size and weight of the screwdriver and requires detent balls to retain it in the bore.